Method of removing broken studs



Dec. 25,- 1945.

FIG.

mm AE .Rm EFH y F D w T 4 Dec. 25, 1945. E. A. FUGLIE l 2,391,405

I METHOD OF REMOVINGr BROKEN STUDS Filed oct. 28, 1942 2 sheets-sheet 2, l

25 f FIG. lo.

ELMER A. FUGLIE I Patented Dec. 25, 1945 l PAT E NT FFI C Y Y y n 2,391,4115 k METHOD 'oF nMovING BROKEN s'rUDs einer Aiiiigiid Winona, 'assigner `to vvi- Tool M f'g.Company, Winona, Minn.,

corporation of Minnesota Application October 28, 1942, S'elia-l No'. 463,722 f2 'Clarins (ci. tipi-4t) My invention relatesto a method of removing broken studs and has lfor its object to .provide a series of steps 'for conveniently and efficiently reniving broken studs kwhile leaving the threaded studv hole in 'condition to receive a new stu'dbolt.

`There 'are many appliances wherein one mein'- bei'V is `secured to another by meansof stud bolts, thebolt extending through the member which is secured and being threaded 'at its 'end and screwed into a threaded hole in the member to which it is attached. A common example of very Wide useA of such Ja form of securing two members togethjeris the cylinder head casing of gas engines, particularly automobile gas engines. Under such conditions, )not infrequentlyy the stud bolt .will break, usually at the top of the hole, leaving the end o f the boltcommonly referred to as a stud, threadeddinto the hole.t Ordinarilythere will be no pari-cf the stud projectingoutside ofthe hole to a sufllcient extent to permit any kindrof ktool topbmer engaged with it to turn out the stud. The practioeqhas been to use a drill directly upon the end ofmthe `Stud ov f a size Vthat Awould -simultaneosly take out the stud and thethreads oi'y .the hola, then.. ijretefp the Yhele .and employ a larger size kstud bolt, which necessitated reboringv th holes 'le .the member@ ,be Securd, .Such as the. vlinder heed 'of `eutwireline engines. rms PlOFdllr?. 1.13.5 not .been salsfaqtqy, bQlhe' lletRVQIYBS a' lafgxmolmtpflafb?? @and liceale@ dig-@Geldes are ,eneuiltered 11.1 drilling ,out thesitdarid thethreads @if` ,the 11o-learn reborine fligholesihfough .th itehed par?. 111..,eettir1e these. hlee il. perfect. al'inemeet- This. is in par due to he faotthat thetwo parts havebeenkept oclated vwhile the respective operations were performed uponfthe'rn. Also it isdiflicult exactly to gentler thedrill iipn the broken end of the stud withthe result 'thatif centering is not accurate.' the lnewly Adrilled hole may Ynot Aline with th 'lifle 'in tthe lother I'rlelloi suoli "als the Cylinder need. have meesteres that 'treten studs can te effectively vremoved "by assembling the parte in niiedfrelatien,introddeing 'in the rio1e`o`fthe top iatfjasleeijze having walls of a 'thiekn'ess equal to fthe depth of the threads of. the 'internally threaded hole, and "using a. i'drill /etending through said sleeve of the diameter df the inside of Vtli'ehole. fntlfismanner the core of the stud will be drilled out without injuring the threads of the stud hole, but leaving the stud threads still in the thread grooves of the stud hole; and following this, by chiseling through a short length across the interthreaded stud threads and vStld h'ole threads and pulling 'out the lt Stud threads for this section, then V'using a tapf to' force the 'Stud threads fioi the 'stud hole 'thread 'grooves which are dropped tothe bottoni stud hole, the stud hole threads are cleared so fa new 'stud bolt oi 'identically 'thesam'e size as Was used beforeean be applied. A

It is, therefore, the object of my invention to remove broken studs Without at the saine -tin' drilling out the threads' 'olf the stud -h'ole so that new stud bolts of identically the saine 'dim`ei1siol1sv may.'Ipltie th broken sltlid b'lt.

In this specicatioh the respective fpart's will be 'referred to as the leylineler bl'ook and cylinder head of 'a gas engine, althoughit Vis 'to be under#- broken studs where stud bolts are used `in any relation to `secure 'two parts together.

'The full 'objects 'and advantages ofv invention will 'appear in fthe specification hereinafter given in detail, and the novel features of 'the V'en'ton by 'Which the 'above#noted advantageous results are obtained are-particularly vpointed out in the claims. y

:In the drawings illustrating the variolis steps orjmy invention andfmethod: A

Fig. l is a sectional view taken through 'a portion f a, cylinder blockand cylinder he'ad, and through the alined holes 'for Securing 'them together by means of a stud bolt showing a broken Stud section.

Fig. 2 is 'a View 'similar to Fig. 1-, lshowing the first step of my process, namely, the "positioning o'f 'a V'sleeve the hole through the wall o'f the cylinder head, saidsleeve having wall thicknesses equal 'to the 'depth 'of the 'threads of the ="s`tud and the `-stud hole.

Fig. 3 is a perspective viewfof vthis fsleeve. 1

Fig,-4 illustrates the lstep of operating adriill through the sleeve, the drill having a 'cutting diameter the Same the internal diameter fof the sleeve.

Fig. -5 is a sectional view showing the cylinder block after the head block has 4been removed "with thelstud 4threads/ in 4position in the thread Vgrooves of "the cylinder block.

fFig. "6 is a sectionalview of theicylinderiblock through a `h0le therein, illustrating tllest "o'f chiseling `through'a-l'liinited number vof thread'st the top of Ytheel-roleinthe cylind'erlblockitoperiit removal of enough stud threads to enable a tap to operate thro-ugh the rest of the hole.

Fig. 7 is a sectional view similar to that of Fig. 6, showing removal of some of the topk stud threads.

Fig. 8 is a sectional view of the cylinder block through a hole therein, showing the tapping out of the remainder of the stud threads.

Fig. 9 is a sectional View similar to Fig. 8, showing the threaded hole into the cylinder block freed of stud threads and ready to receive a new stud bolt.

Fig. 10 is an end view of the cutting tool shown in Fig. 6.

Referring now to the drawings, a cylinder block I is formed with the customary stud bolt holes I I internally threaded as indicated at I2. A broken stud shank I3 is shown in Figs. 1 and 2. The upper end I4 of /said stud shankis shown, as is customarily true of broken stud bolts, as substantially in the plane of the top I5 0f the cylinder block I3. The head block I5 is shown in Figs. 1, 2 and 3, as in position upon the cylinder block I with bolt hole l1 extending through it and in alinement with internally threaded hole II in the cylinder block III. In this connection it will be noted that the bolt hole I1 has a transverse diameter, such that the walls thereof coincide with the bottoms of the threads I2 in stud bolt holesl II. A stud bolt, not shown, is therefore of a diameter substantially that of the stud bolt hole I'I and is threaded into `the stud bolt hole I-I as is the broken stud end I3 shown in Figs. 1 and 2.

In the practice of my invention, while the head block I 6 is secured upon the cylinder block I0 so that bolt hole I 'I therethrough is centered about broken stud end I4, a sleeve I8 is introduced in bolt hole II. As clearly indicated in Figs. 2 and 4, this sleeve has its circumferential wall of a thickness exactly equal to the depth of the threads I2 on the inside of stud bolt hole II. That is, the cylinder outlined by the inner wall of sle'eve I8 coincides with the cylinder outlined by the top of the threads I2. Sleeve I8 also is preferably of a length such that its upper edge I9 coincides with the top of the boss 20, customarily surrounding the top of bolt hole II.

As the next step in my method, a drill bit 2| is inserted within sleeve I8. The bit 2l has a diameter substantially that of the internal diameter of sleeve I8 which thus holds the bit perfectly centered upon the broken top I4 of stud end I3. It follows that operation of the drill will remove the body of the stud end I3, leaving a perfectly centered hole 22, which has its circumferential wall coinciding with the outer limits 23 of the threads I2 in bolt hole II. There is left then, as shown in Fig. 5, only the bolt threads 24 which formed a part of the stud end I3'.

These threads then must be removed to permit a new stud bolt to be screwed into the bolt hole II. The next stepin my process consists in the removal of these threads. This is accomplished, as shown in Fig. 6, by the use of a cutting tool 25. This tool, Fig. 10, is provided with a cutter portion 26 having a V-shaped cutter edge 2'I disposed at a slight angle as indicated at 28 in Fig. 6. By the use of a hammer or mallet the cutter is driven downward as indicated in dotted lines at 29, Fig. 6, where it has forced its Way through so as to cut across some four of iive of the threads 24 remaining in the grooves of threads I2. After this cutting has been effected, the cut threads are pulled out by suitable appliances, leaving exposed a number of threads I2 as shown in Fig. 7. These threads I2 have been cut across as indicated at 3D in Fig. 7, but this does not interfere with their utility to permit a threaded member, as a bolt or a tap, to be screwed upon them.

In the iinal step of my process I employ a tap 3| of common construction of the same thread pitch and diameter as that of the internal threading of stud bolt hole I I. The remaining threads 24 are thus forced out of thread grooves I2 and fall into the space below the lowest extent of stud bolt I3, as indicated at 32, Where they can be permitted to remain, or if it is deemed desirable to withdraw them that can be done readily by the use of a circular magnet put down into the bolt hole for that purpose. After the tapping operation the bolt hole I I will have all its internal threads free and ready to have a stud bolt screwed upon them as indicated at 33 in Fig. 9.

The advantages of my invention will be apparent from the foregoing description. By the practice of my invention, broken stud bolt ends may easily be removed with absolute accuracy, leaving the internal threads of the bolt hole free and undamaged for receiving the threads of a new stud bolt. This is accomplished without expensive apparatus and has the Very great merit of requiring a relatively small amount of labor and none of that highly skilled labor.

I claim:

1. The method of removing broken stud bolt ends, which consists in holding the member adapted to be fastened by the stud bolt with its bolt hole in normal position over the broken stud bolt end, applying inY said hole a sleeve having an outer diameter substantially that of the hole and an inner diameter that of the cylinder outlined by -the bottoms of the stud threads, guiding -a drill bit of substantially the diameter of the inner diameter of the sleeve through said sleeve to center the bit upon the top of the broken end, operating the drill to remove the body portion of the stud end so as to leave the threads separated and in the threads of the stud bolt hole, and thereafter removing the separated threads to leave the bolt hole threads free end ready to receive a stud bolt.

2. The method of removing broken stud bolt ends, which consists in holding the member adapted to be fastened by the stud bolt with its bolt hole in normal position over the broken stud bolt end, applying in said hole a sleeve having an outer diametersubstantially that of the hole and an inner diameter that of the cylinder outlined by the bottoms of the stud threads, guiding a drill bit of substantially the diameter of the inner di.- ameter of the sleeve through said sleeve to center the bit upon the top of the broken end, operating the drill to remove the body portion of the stud end so as to leave the threads separated and in the threads of the stud bolt hole, cutting through a plurality of said separated threads from the top down, removing the cut threads to expose a section of upper bolt hole threads and thereafter applying a tap of suitable diameter and pitch to the exposed bolt hole threads and operating the tap to force out the remainder of the bolt threads to leave the bolt hole threads free and ready to receive a stud bolt.

ELMER A. FUGLIE. 

